Sometimes it's impossible to nail down exactly why a certain cocktail suddenly explodes in popularity. Other times, it's as simple as a single word: Oprah. Yes, ever since America's BFF announced that the Moscow Mule was her (and Gayle's) drink du jour, sales of this copper-clad classic have gone through the roof.

"The Moscow Mule is by far our number one selling cocktail this year," says Dale Jodowin, general manager at the landmark Scottsdale lounge, AZ 88. "It's always sold well, because it's so refreshing here in a sunshine state. But before Oprah it was maybe our 10th or 12th bestselling cocktail."

However, there's more to this 70-year-old recipe than its crisp taste, celebrity cache and even its gimmicky copper mug. In fact, the Moscow Mule might have been the most successful marketing stunt in history, almost singlehandedly transforming America from the land of gin and whiskey, to a nation of vodka sippers.

Drink up after the jump.

In the Beginning While there are various versions of how the Moscow Mule was invented, most people agree it all started in 1941 in Manhattan, when (stop me if you've heard this before) three men walked into a bar. Two were in the vodka distributing business, while the third owned a popular L.A. watering hole named Cock 'N Bull, and happened to sell ginger beer on the side. They started playing around with a vodka-based twist on a classic mixed drink called a 'Buck,' or a 'Mule,' which involved mixing ginger ale or ginger beer, citrus juice, and any of a number of liquors, including rum, whiskey, bourbon, or gin. (Drop a lime into a Dark 'N' Stormy and you've got a Rum Buck.)

Needless to say, the Moscow Mule was a hit, especially after Hollywood stars were spotted sipping it at the Cock 'N Bull pub on the Sunset Strip. And driven in part by the popularity of the Mule, vodka eventually supplanted gin as the "dominant white spirit in the United States," according to the Beverage Tasting Institute.

It also helped that vodka was less noticeable on your breath than gin's distinctly-herbal bouquet. (Which is important when you're knocking back one of those Mad Men-style three-martini lunches.) No wonder why Smirnoff, the original vodka in a Moscow Mule, was marketed with the classic double entendre tagline: "Smirnoff -- It leaves you breathless." (See the Woody Allen ad at right.)

Finally, what's the deal with the Moscow Mule's old-timey copper mug? Again, no one knows for sure, but most agree with AZ 88's Dale Jodowin that it was all part of the drink's clever marketing scheme. "Reportedly, the owner of the Cock 'N Bull, or one of his good friends, had a warehouse full of copper mugs that was just sitting around collecting dust."

Cheesy gimmick or not, the copper mug certainly adds to the Moscow Mule's cache. "Thanks to copper's conductive properties, it feels much colder in your hand than the same drink served in a glass cup," Jodowin says. "Plus it just looks cool."

Where To Find ItAZ 88 has been serving its own twist on this classic cocktail for more than 20 years. Made with Stolichnaya vodka, fresh lime and traditional Cock 'N Bull ginger beer, it's also given a crisp, quenching twist thanks to the addition of fresh cucumber puree.